2021_NJC_Prelim_P1_Ans

1 8873/01 [Turn over NATIONAL JUNIOR COLLEGE SH 2 PRELIMINARY EXAMINATION Higher 1 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Multiple Choice Answer Sheet Data Booklet 8873/01 Wednesday 15 September 2021 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name, subject class and registration number on the Answer Sheet in the spaces provided unless this has been done for you. There are thirty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet. Read the instructions on the Answer Sheet very carefully. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. Instructions on how to fill in the Optical Mark Sheet Shade the index number in a 5 digit format on the optical mark sheet: 1st digit and the last 4 digits of the Registration Number. Example: Student Examples of Registration No. Shade: 2005648 25648 This document consists of 12 printed pages.

2 8873/01 [Turn over 1 Which statement about 1 mol of a metal is always true? 1. It has the same number of atoms as 1 mol of hydrogen atoms. 2. It loses 1 mol of electrons. 3. It contains half the number of atoms as 2 mol of HCl(g). 4. It contains 1 3 the number of ions as 3 mol of Na2O(s). A 1 B 1 and 3 C 1, 2 and 3 D 1, 3 and 4 1: Correct. 2: Incorrect. Different metals liberate different moles of electrons. Eg 1 mol of Mg is liberated by 2 mol of electrons. 1 mol of Na is liberated by 1 mol of electrons. 3: Incorrect. 2 mole of HCl(g) contain 4 moles of atoms. 4: Incorrect. 1 mole of Na2O contain 3 moles of ions. For 1/3 of 3 moles of Na2O, there are 3 moles of ions. Answer: A 2 The actual values of the masses of three sub-atomic particles are shown in the table. proton neutron electron mass/kg 1.673  1027 1.675  1027 9.109  1031 Which nickel ion is predicted to have a mass of 1.038  1025 kg from these data? A 𝑁𝑖28 60 2+ B 𝑁𝑖28 62 2+ C 𝑁𝑖28 58 3+ D 𝑁𝑖28 64 3+ No. of protons No. of neutrons No. of electrons 𝑁𝑖28 60 2+ 28 60 – 28 = 32 28 – 2 = 26 𝑁𝑖28 62 2+ 28 62 – 28 = 34 28 – 2 = 26 𝑁𝑖28 58 3+ 28 58 – 28 = 30 28 – 3 = 25 𝑁𝑖28 64 3+ 28 64 – 28 = 36 28 – 3 =25 Mass = 28(1.673  1027) + 34(1.675  1027) + 26(9.109  1031) = 1.038  1025 kg Answer: B

3 8873/01 [Turn over 3 The redox half-equations for the electrolysis of dilute sodium chloride solution are stated below. Oxidation half-equation: 2H2O → O2 + 4H+ + 4eˉ Reduction half-equation: